This application claims benefit of Japanese Application Number 2000-270614 filed on Sep. 6, 2000, the contents of which are incorporated by this reference.
1. Field of the Invention
The present invention relates to a self-igniting engine by igniting an air fuel mixture at multi-points.
2. Description of the Related Art
So far, there have been studied various types of engine operating techniques, for example, not only operating by a spark ignition but also by a self-igniting engine using a compression heat in dependency on a driving range for controlling an emission of toxic gases from a gasoline engine. In the case of such a self-igniting engine, although the quantity of NOx to be generated in an emission gas is considerably reducible, difficulty is encountered in positively controlling the ignition timing as well as an ordinary spark ignition type gasoline engine because the combustion depends on the self-igniting method.
Such a conventional self-igniting type engine has been disclosed in Japanese Unexamined Patent Publication No. 11-210539. In the case of the self-igniting type gasoline engine disclosed in this Publication, the gas temperature (air fuel mixture temperature) for igniting the air fuel mixture within a combustion chamber is set to a little lower temperature than a temperature causing the self-igniting, and the air fuel mixture is ignited by spark plug within that range by increasing the internal pressure in the cylinder by the combustion of the air fuel mixture around the spark plug for increasing the gas temperature therein as whole, thereby multi-point-igniting the entire air fuel mixture.
However, in a case where the self-igniting timing is controlled by the ignition timing of the spark plug like this as disclosed in the aforesaid publication, there is a need to control the air fuel mixture temperature to be within a ignition temperature range which is impossible for self-igniting. For example, in a case where the air fuel mixture temperature reaches the temperature which does not rely on sparking, knocking occurs due to early ignition. On the other hand, when the air fuel mixture temperature falls below that temperature relying on the sparking, a misfire occurs. For this reason, difficult is the control of the air fuel mixture temperature. In addition, difficulty is experienced in changing the air fuel temperature rapidly, which makes it difficult to offer a stable combustion state.
Accordingly, it is an object of the present invention to provide a self-igniting engine capable of achieving a stable combustion state in a self-igniting operation range by controlling the fuel injection timing to overcome a difficulty of controlling the air fuel mixture temperature.
In accordance with the present invention, there is provided a self-igniting engine including fuel injection means for injecting a fuel directly into a combustion chamber, temperature increasing means for increasing a temperature of an air fuel mixture by evaporating the fuel to a self-igniting possible temperature causing a multi-point ignition, and injection timing control means for setting a fuel injection start timing in the middle of an intake stroke for a low-load operating condition and for setting the fuel injection start timing in the first half of a compression stroke for a high-load operating condition.
In this configuration, in a compression ignition driving range where there occurs multi-point ignition of premixed air fuel made by the evaporation of a fuel directly injected from the fuel injection means into the combustion chamber, temperature increasing means increases the air fuel mixture up to a compression ignition possible temperature, while the injection timing control means sets the fuel injection start timing in the middle of an intake stroke at a low-load driving and sets it in the first half of a compression stroke at high-load driving.
The above and other objects, features and advantages of the invention will become more clearly understood from the following description referring to the accompanying drawings.